Exploring Lung Cancer Metabolome: From Bench to Bedside

Professor, Department of Toxicology and Cancer Biology
University of Kentucky

Exploring Lung Cancer Metabolome: From Bench to Bedside

Abstract:

The past decade of research in cancer metabolism reveals the value of exploring human metabolome for the discovery of novel therapeutic and diagnostic biomarkers for human cancers and other diseases. Using 13C6 glucose as tracer and NMR and MS-based stable isotope-resolved metabolomics (SIRM) analysis, we defined metabolic reprogramming in lung tumor tissues in vivo in 59 human patients with early stage NSCLC. In particular, we uncovered elevated anaplerotic pyruvate carboxylase (PC) activity in cancerous against paired benign tissues. Proliferating cancer cells require an active Krebs cycle for generating anabolic precursors, in addition to energy production. Diversion of the Krebs cycle intermediates to meet anabolic demands cannot be sustained without anaplerosis. Pyruvate carboxylation represents one of the two major anaplerotic pathways that support cancer cell growth; the other involves glutaminolysis initiated by glutaminase (GLS). We then measured the expression of PC and GLS proteins in tumor and benign tissue pairs from 86 human NSCLC patients. PC protein was elevated (median 8-10 fold) in 94% of the tumor tissues, whereas GLS expression did not differ significantly between tumor and benign tissue pairs. We further examined the importance of PC in the growth and survival of NSCLC by employing the shRNA knockdown approach to demonstrate reduced lung cancer cell growth both in vitro and in vivo. PC knockdown not only attenuated PC-initiated Krebs cycle activity but also glutamine metabolism, as probed by 13C6-glucose and 13C5,15N2-glutamine tracers coupled with SIRM analysis. These effects in turn led to reduced anabolic activity such as synthesis of fatty acyl chains of lipids, suggesting that both energy production and anabolic pathways were hindered and blocking the PC pathway was not compensated by GLS activity. Applying the SIRM approach to ex vivo lung tissue slice cultures indicated that blocking PC anaplerosis with anti-cancer Se compounds can elicit massive necrosis in cancerous but not in benign lung tissues. Together, these results suggest PC can be a promising therapeutic target for lung cancer.

Bio:

My research focuses on applying novel Stable Isotope-Resolved Metabolomic (SIRM) and metabolomics-edited transcriptomic approaches (META) which we have developed 1) to investigate the anticancer mechanism of natural products and novel therapeutic agents, 2) to explore the functional role(s) of tumor microenvironment and extrinsic environmental factors in disease development, progression, and therapy, and 3) to uncover novel therapeutic targets and distinct functional biochemical marker patterns for human diseases by interrogating the human metabolome. The central tool that I have used to achieve the goal is the integration of nuclear magnetic resonance (NMR) with mass spectrometry (MS) technologies, which enables a systematic interrogation of human metabolic networks and their perturbations by diseases. Since 2006, I established and directed a state-of-the-art MS facility under the auspices of the Center for Regulatory and Environmental Analytical Metabolomics (CREAM) while at the University of Louisville. Under my direction, CREAM developed several novel techniques for analyzing pathways of central metabolism including amino acid, carbohydrate, lipid, nucleotide, protein, and anti-oxidant metabolism in cancer. With the SIRM tool and systems, I have uncovered persistent activation of pyruvate carboxylation in vivo in human lung cancer tissues in early developmental stages and demonstrated that inhibition of this mitochondrial anaplerotic pathway intoxicates lung cancer cells but not normal cells. I have also defined metabolic dysregulations induced by different anti-cancer selenium agents and unraveled the metabolic basis (e.g. perturbed mitochondrial metabolic networks and nucleotide metabolism) for the varying efficacy of these agents in chemopreventive clinical trials. My long-term goal is to continue an integrated ‘omics approach to translate mechanistic understanding of human diseases and influences of macro- and microenvironmental factors on disease etiology into clinical benefits such as prevention, early detection, prognosis, and discovery of molecular targets leading to efficacious individualized therapy. With the recent move of CREAM to the University of Kentucky to establish a new Center for Environmental and Systems Biochemistry (CESB) along with a U24-funded NIH metabolomic resource center (RCSIRM), instrumentation and informatics capabilities are greatly expanded to facilitate the fulfillment of my research goals and to further expand our educational and collaborative capacity.